Marine propeller having a buoyant chamber



u 10, 1969 I c. w. HERBERT 3,448,715

MARINE PROPELLER HAVING .A BUOYANT CHAMBER Filed Feb. 21. 1967 snet of 4 June 10, 1969 I .W. EB T 3,448,715

MARINE PROPELLER HAVING A, BUOYANT CHAMBER v Filed Feb. 21', 19 s? Sheet 3 of 4 June 10, 1969 c. w. HERBERT 3,448,715

MARINE PROPELLER HAVING -A BUOYANT CHAMBER Filed Feb. 21, 1967 Sheet 3 of 4 June 10, 1969 c, w, HERBERT 3,448,715 l MARINE PROPELLER HAVING A BUOYANT CHAMBER Filed Feb. 21, 1957 Sheet of 4 Q g I I Q 1 l 2 I I I III I I I I I I I I i 1' 1 w m l N I L H. N 3 N United States Patent 6 Int. Cl. B63h 1/38, /06

U.S. Cl. 115-34 3 Claims ABSTRACT OF THE DISCLOSURE A marine propeller has a buoyant chamber attached to its aft end to reduce the bending moment on the shaft where it passes through the stern bearing. The buoyant chamber is a closed shell filled with closed-cell foam to prevent access of water in the case of damage to the shell. To give maximum support to the shaft the buoyant chamber is of slightly tapering external form and truncated at its aft end.

The present invention relates to marine propellers. The mounting of a large heavy propeller on the aft end of the propeller shaft in conventional manner gives rise to substantial bending moments on the shaft and places a substantial load on the bearings supporting the shaft.

In accordance with the present invention there is provided a marine propeller with a boss which has at its aft end a buoyancy chamber providing a lifting moment acting in opposition to the weight of the propeller.

In a preferred embodiment the buoyancy chamber is a detachable closed hollow body in the form of a shell of reinforced plastic filled with a foam material having a closed cell structure.

Preferably the present invention is used in conjunction with a propeller of the kind described in a co-pending application which has a boss in the form of a hollow cylinder with an internal flange for attachment to an end flange on the propeller shaft. This form of propeller boss likewise serves to reduce the bending moments on the propeller shaft since the weight of the propeller is carried forward around the shaft and the bearing supporting the shaft can extend closer to the centre of gravity of the propeller.

The invention will now be described in more detail with the aid of examples illustrated in the accompanying drawings, in which:

FIGS. 1A and 1B are respectively a side elevation and plan of a propeller assembly in accordance with the invention,

FIGS. 2A and 2B are respectively a side elevation and plan of modification of the assembly of FIGS. 1A and 1B,

FIGS. 2C and 2D are respectively a side elevation and a plan of a further modification of the assembly of FIGS. 1A and 1B, and

FIG. 3 is a longitudinal section of a propeller in accordance with the invention.

FIGS. 1A and 1B show a propeller mounted on the aft end of a propeller shaft (not shown) extending from a stern frame 11 of a ship. A rudder 12 is mounted in conventional manner aft of the propeller 10. The propeller has a boss 13 which carries a buoyancy chamber 14 of generally cylindrical form extending close to the rudder 12. The profile of the buoyancy chamber 14 prolongs that of the propeller boss 13 with a progressivelyice increasing taper but is truncated at the aft end where its diameter is still greater than half the diameter at the boss. The buoyancy chamber 14 provides an upthrust exerting a lifting moment in opposition to the weight of the propeller 10. For this purpose it is desirable to keep the diameter of the buoyancy chamber 14 at its aft end as large as possible in order to increase the moment of the buoyancy about the shaft bearing.

In FIGS. 2A and 2B the rudder 12 is recessed at 15 to receive the aft tend of the chamber 14, thus enabling the rudder to be kept close to the propeller while using a buoyancy chamber 14 with a substantial axial length. The chamber 14 has a small angle of taper. Its profile is continued by a fairing 16 on the rudder to smooth the flow of water around the propeller and rudder. Alternative profiles are shown in broken lines.

The propeller assembly of FIGS. 2C and 2D corresponds to that of FIGS. 1A and 1B in having a halfbalanced rudder but has the buoyancy chamber 14 accommodated in arecess 15 bounded by a curved wall 15a. The rudder is thus brought as close to the propeller as possible while obtaining significant buoyancy from the chamber 14 and good streamlining.

FIG. 3 shows the construction of the propeller 10 and the chamber 14. The boss 13- is a hollow cylinder having an internal annular flange -17 which is secured to an end flange 18 of a propeller shaft 19. The weight of the propeller can be further forward than in designs in which the boss is carried directly on the shaft or has its forward end attached to the aft end of the shaft. The aft end of the boss 13 is fitted with a transverse sealing wall 20. The buoyancy chamber '14 consists of a rigid shell 21 of synthetic resin reinforced with glass fibre and a body 22 of rigid foam plastic having a closed cell structure filling the shell 21. Metal strengthening plates 23 are embedded in the Walll of the shell 21 and the shell is bolted to the aft end of the propeller boss 13 by bolts 14.

The shell 21 can be fabricated from sheet metal or from synthetic or natural elastomers, vulcanised or unvulcanised. The foam body 22 can be of polyurethane or other synthetic material which produces a light foam with a closed cell structure. The closed cell structure is desirable in case of damage to the shell since it prevents flooding of the whole of the interior of the buoyancy chamber. The foam can be formed in situ and serves to give support to the wall of the shell. Alternative methods of fixing the buoyancy chamber to the propeller can be used but are preferably always such as to enable the buoyancy chamber to be removed for access to the propeller for removal and inspection.

I claim:

1. A marine propeller having a boss, a buoyant chamber attached to the aft end of said boss, said buoyant chamber being of slightly tapering external form, and truncated at its aft end, said aft end of said buoyant chamber extending substantially perpendicular to the axis of said buoyant chamber, said aft end of said buoyant chamber having a diameter greater than about half the diameter at said boss, said buoyant chamber being a closed hollow body, and a filling of closed-cell foam material within said hollow body.

2. A marine propeller as claimed in claim 1 in which the closed hollow body is a shell of reinforced plastic.

3. A marine propeller as claimed in claim 1 wherein the boss is in the form of a hollow cylinder having an internal flange for attachment to an end flange on the propeller shaft.

(References on following page) 3 4 References Cited 2,987,123 6/1961 Liaaen 170-16023 UNITED STATES PATENTS 3,132,417 5/1964 II'Will 9-8 X 794,932 7/1905 Fullerton. FOREIGN PATENTS 1,834,003 12/1931 Oertz 114-162 1,022,792 8/1950 Fra 2,028,448 1/1936 Harza 170-16023 X 5 51,361 8/1932 Norway, 2,283,291 5/1942 Selden 114-162 X 2,470,517 5/ 1949 Obrist 170-16024 TRYGVE M. BLIX, Primary Examiner.

2,933,141 4/1960 Kapsenberg 170-160.23 

